As a diaphragm valve, there is a known type including a body provided with a fluid channel, a seat demountably arranged in a peripheral edge of the fluid channel formed, on the body, a seat holder demountably arranged on the body and configured to hold the seat, a diaphragm configured to open and close the fluid channel by being pressed against or moved away from the seat, a diaphragm holding member configured to clamp an outer peripheral edge portion of the diaphragm with the seat holder, a vertically moving device configured to move the diaphragm holder configured to press a center portion of the diaphragm upward and downward (Patent Literature 1, and so forth).
In the diaphragm valve of the related art as described above, the seat is demountable and is held by the seat holder, and the seat itself can be replaced when having become damaged.